Plates are typically large substrates that have been coated with photosensitive or thermally-sensitive material layers. Depending on the type of plate, they can be sensitive or insensitive to ambient light. The plates are usually used in commercial printing operations. For large run applications, the substrates are fabricated from aluminum, although organic substrates, such as polyester or paper, are also available for smaller runs. Because of the composition, the plates can be somewhat heavy, especially in the context of a stack of relatively large plates.
Computer-to-plate printing systems are used to render digitally stored print content onto these printing plates. Typically, a computer system is used to drive an imaging engine of a platesetter. The engine selectively exposes the surfaces of these plates. In a common implementation, the plate is fixed to the outside or inside of a drum and then scanned with a modulated laser source in a raster fashion.
Typically, one of two different strategies is used to feed the plates to the imaging engine. In the simplest case, an operator manually places individual plates into a feeder that then conveys the plates through a feed port to the drum scanner. This approach, however, has some obvious drawbacks, since an operator must be dedicated to feeding the plates. Moreover, the printing system must be housed within a light-safe environment, if the plates being used have any sensitivity to ambient light. The alternative approach is to use a plate manager.
Plate managers typically house multiple plate cassettes. Each cassette holds tens of plates in a stack. For example, in one common implementation, each cassette holds about thirty to fifty plates. The plate manager selects plates from one of its cassettes and then feeds the plates, automatically, into the imaging engine.
In these designs, cassettes are loaded into the plate manager on separate tables. The tables are then raised and lowered inside the manager to bring the plates of a selected cassette into cooperation with a plate picker that grabs individual plates and feeds them to the imaging engine.
In some applications, the plates can be shipped and stored in these cassettes. In other cases, the plates are shipped to the end user in a crate and then transferred to the cassettes by an operator.